Fiona's second puberty starts

"Come on, Doug, Measure me!" Fiona said, poking her boyfriend.

"We did it a week ago, how could you possibly have grown since then?"

Her smug smile did not falter for a second. "Measure me!"

Doug sighed. "Fine."

With an excited jump, Fiona pushed herself against the wall of her room, while Doug took a stool. Standing on it, he was just able to reach the top of her head and get a measurement. "You are..." He was about to say, before his jaw dropped. He checked he was measuring her correctly, then he checked again. Finally, defeated, he announced: "You are a smidge under 6'5. You have grown almost a full inch in a week. What the hell? How is that even possible?"

"Yes! I knew it! This is so cool, Doug. I'm so happy!" She said, hugging her boyfriend tightly.

"Ok, ok!" Doug said, trying to free himself from the affectionate ****. "Calm down, but seriously, how? You are 18, puberty was done years ago, how are you growing this quickly?"

"Family secret" Fiona said. Seeing the confusion on Doug's face made her smile grow even wider. She finally put him down and continued: "You have probably noticed my mother is a lot taller than me and my sister, right? That's because futa in our family go through a second puberty around 18 to 20 years old. It's actually a rare genetic mutation that occurs once every 5.000 futas. A lot of top level athletes have it. My mother had hers just before she had me, and she was shorter than me when it started, can you imagine how tall I will be at the end? I cannot wait!"

"Wait, slow down, are you serious? You're just going to grow taller now?"

"Not just height, it's a full puberty. My boobs will grow too, and my dick probably as well. And of course my hormones will go crazy so my sex drive will probably go in overdrive. It's not by chance that my mother had me just after her second puberty ended."

Doug gulped. She loved his girlfriend, but she was already a handful now, he was honestly worried about her growing giant-er and hornier, if that is even possible. She was already 9 inches taller than him, not to mention much bigger downstairs.

While he was busy thinking, he failed to notice his girlfriend advancing towards him. She pinned him against the wall, her eyes full of lust, her hips grinding against him. Soon, her cock woke up. "God, you're already so small. I can't wait before you're under my boobs. Fuck! I don't understand why is that so hot, but I love it. You love it too, right Dougie?" She said, while her huge erection rubbed against his abdomen.

"O-Of course, Fiona. I can't wait." He was not lying, he did like their height difference, his hesitation was born out of fear of not being enough for his growing girlfriend.

But Fiona did not hear him, she was lost in her fantasy. The younger futa humped him with wild abandon, enough that Doug's skin was getting irritated by the friction. He could do nothing but hope that she would come to her senses soon, however, he could do nothing against her superior strength.

Fortunately for him, she was already so excited that her climax came soon. With a last thrust, she tensed up and her cock exploded against him, coating his shirt with white strands of cum. More and more poured out, some reaching his face and her boobs. It was only when her orgasm ended that she realized what she had done. "Oh shit, I'm sorry. I got... a little carried away."

"I noticed" Doug said, wiping cum off his face.